From 058b3c914b59a3915dc57c416e28e4c54fd467fc Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Sat, 26 Aug 2023 10:52:40 +0200
Subject: [PATCH] add $PVXS_ENABLE_IPV6

---
 src/evhelper.cpp | 13 ++++++++++++-
 src/evhelper.h   |  3 ++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/evhelper.cpp b/src/evhelper.cpp
index 43d233a33..da253daf3 100644
--- a/src/evhelper.cpp
+++ b/src/evhelper.cpp
@@ -21,6 +21,7 @@
 
 #include <errlog.h>
 #include <epicsEvent.h>
+#include <epicsString.h>
 #include <epicsThread.h>
 #include <epicsExit.h>
 #include <epicsMutex.h>
@@ -661,9 +662,19 @@ size_t evsocket::get_buffer_size(evutil_socket_t sock, bool tx)
 #  define EAFNOSUPPORT WSAESOCKTNOSUPPORT
 #endif
 
-bool evsocket::init_canIPv6()
+bool evsocket::init_canIPv6() noexcept
 {
     try {
+        if(auto ena6 = getenv("PVXS_ENABLE_IPV6")) {
+            if(epicsStrCaseCmp(ena6, "NO")==0) {
+                log_info_printf(logsock, "IPv6 support disabled%s", "\n");
+                return false;
+            } else if(epicsStrCaseCmp(ena6, "YES")!=0) {
+                log_warn_printf(logsock, "PVXS_ENABLE_IPV6=%s ignoring unrecognized\n",
+                                ena6);
+            }
+        }
+
         evsocket sock(AF_INET6, SOCK_DGRAM, 0);
         auto addr(SockAddr::loopback(AF_INET6));
         sock.bind(addr);
diff --git a/src/evhelper.h b/src/evhelper.h
index d2cea97c1..ab0f552a9 100644
--- a/src/evhelper.h
+++ b/src/evhelper.h
@@ -255,7 +255,7 @@ struct PVXS_API evsocket
     static
     bool canIPv6;
 
-    static bool init_canIPv6();
+    static bool init_canIPv6() noexcept;
 
     enum ipstack_t {
         Linsock,
@@ -302,6 +302,7 @@ struct PVXS_API IfaceMap {
         Iface(const std::string& name, uint64_t index, bool isLO) :name(name), index(index), isLO(isLO) {}
     };
 
+    SockAttach attach;
     epicsMutex lock;
     std::map<uint64_t, Iface> byIndex;
     std::map<std::string, Iface*> byName;